The Advanced LIGO detectors at the beginning of the new gravitational wave era Lisa Barsotti MIT Kavli Institute LIGO Laboratory on behalf of the LIGO Scientific Collaboration LIGO Document G1600324
LIGO Scientific Collaboration
In this talk The Advanced LIGO detectors Plans towards the next observing run Growing the gravitational wave network What s next going beyond Advanced LIGO August 6, 2016 - ICHEP L. Barsotti 3
Gravitational waves cause strain distortion of spacetime, Michelson interferometer can measure it GW Amplitude h ~10-21 Credit: ESA δly DL = h L =10-21 4000 = 4 10-18 m Amplitude of the gravitational wave Strain over distance L August 6, 2016 - ICHEP L. Barsotti 4 L DL L = dl -dl x y L = h δlx
Advanced LIGO: 2 twins 4 km laser interferometers LIGO Hanford Observatory (Washington State) H1 detector Photo Credit: R. Ward, S. Ballmer LIGO Livingston Observatory (Louisiana) L1 detector August 6, 2016 - ICHEP L. Barsotti 5
The Advanced LIGO detectors 40 kg fused silica optics very high optical quality NPRO CW Laser d:yag @ 1064nm up to 200W Up to nearly 1 MW in each arm at full power to reduce quantum noise about 100 kw during O1 Photo-detector August 6, 2016 - ICHEP L. Barsotti 6
est mass suspended by a quadruple pendulum, attached to two stages of active isolation to reduce seismic noise Final stage of test mass suspension all fused silica, very high quality factor, designed to reduce thermal noise Test masses have dielectric coating material with low mechanical loss to reduce thermal noise August 6, 2016 - ICHEP L. Barsotti 7
The Advanced LIGO detectors More than 300 control loops needed to keep the interferometer optimally running Interferometer noise + gravitational wave signal August 6, 2016 - ICHEP L. Barsotti 8
GW 150914 August 6, 2016 - ICHEP L. Barsotti 9
Interferometer Displacement Noise TECHNICAL NOISE SEISMIC NOISE THERMAL NOISE QUANTUM NOISE H1 detector GW150914: The Advanced LIGO Detectors in the Era of First Discoveries (Phys. Rev. Lett. 116, 131103) August 6, 2016 - ICHEP L. Barsotti 10
Many noise sources in the 10-100 Hz band Sensitivity of the Advanced LIGO detectors at the beginning of gravitational wave astronomy D. V. Martynov et al. Phys. Rev. D 93, 112004 August 6, 2016 - ICHEP L. Barsotti 11
Strain noise during O1: better than ever, not at design sensitivity yet Strain Noise = Detector noise expressed as equivalent GW strain Initial LIGO (2010) Advanced LIGO Design Sensitivity of the Advanced LIGO detectors at the beginning of gravitational wave astronomy D. V. Martynov et al. Phys. Rev. D 93, 112004 August 6, 2016 - ICHEP L. Barsotti 12
Observing Run O1 (from mid-september 2015 to mid-january 2016) During O1: H1 and L1 operational for ~4 calendar months Duty cycle: H1 = 62%, L1 = 55% H1&L1 = 43% 51.5 days of coincident time, 48.6 days after data quality process The product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation August 6, 2016 - ICHEP L. Barsotti 13
VIRGO expected to join the network soon 3 km advanced detector Installation nearly completed August 6, 2016 - ICHEP L. Barsotti 14
LIGO-Virgo Observing Plan Overview Live Observing document http://arxiv.org/abs/1304.0670 Binary Neutron Star ranges 65-80 Mpc 80-120 Mpc 120-170 Mpc O1 O2 O3 200 Mpc 2015 2016 2017 2018 2019 August 6, 2016 - ICHEP L. Barsotti 15
Since the end of the first Observing Run O1 Work to improve the sensitivity: Noise hunting : understand and reduce the noise at low frequency Increase the circulating power to reduce quantum noise (several challenges associated with that) Data quality improvements Interferometer robustness August 6, 2016 - ICHEP L. Barsotti 16
(Some of) the challenges with high circulating laser power Thermal lens in the interferometer mirrors induced by high circulating power require active thermal compensation Mirror alignment control Parametric instabilities: acoustic modes of the mirrors get excited and pump light in high order optical modes, that become resonant in the arms Observation of Parametric Instability in Advanced LIGO Matthew Evans et al. Phys. Rev. Lett. 114, 161102 (2015) August 6, 2016 - ICHEP L. Barsotti 17
Projected sensitivity for O2 (this Fall) Projections for O 2 strain noise H1 O1: BNS 75 Mpc, BBH (20/20 Msol) 658 Mpc L1 O1: BNS 69 Mpc, BBH (20/20 Msol) 600 Mpc H1 O2 projection: BNS 87 Mpc, BBH (20/20 Msol) 765 Mpc L1 O2 projection: BNS 87 Mpc, BBH (20/20 Msol) 770 Mpc Strain noise h [1/ Hz] 10-22 10-23 PROJECTION!! 10 1 10 2 10 3 Frequency (Hz) 15-20% improvement August 6, 2016 - ICHEP L. Barsotti 18
Binary Black Holes Rates https://arxiv.org/abs/1606.04856 O2: projected time volume at least 2/2.5 larger wrt O1 Expect to see (at least) a few significant events by the end of O2 Ten(s) of events by the end of O3 surveyed time-volume (shown as multiple of VT analyzed for O1) August 6, 2016 - ICHEP L. Barsotti 19
The upcoming world-wide network of advanced detectors 3 km underground test-bed Michelson successfully locked! 3 km advanced detector Installation nearly completed LIGO-INDIA approved! August 6, 2016 - ICHEP L. Barsotti 20
Can we do better than advanced detectors? LIGO Progression LIGO 2010 10-22 O1 (2015) Strain [1/ Hz] 10-23 Advanced LIGO Design (2019) 10-24 10 1 10 2 10 3 Frequency [Hz] Quantum noise Seismic noise Gravity Gradients Suspension thermal noise Coating Brownian noise Coating Thermo-optic noise Substrate Brownian noise Excess Gas Total noise August 6, 2016 - ICHEP L. Barsotti 21
Beyond advanced detectors Strain 1/ Hz 10-21 10-22 10-23 O1 Advanced LIGO Design A+ Voyager CE Two complementary strategies: better technologies and longer interferometer arms Up to a factor of 2-4 better sensitivity than design in current facility 10-24 10-25 40 km LIGO detector 10 1 10 2 10 3 Frequency (Hz) PRELIMINARY! European design study: Einstein telescope Triangular shape, underground (see: http://www.et-gw.eu/) Ultimately need new facility with longer baseline for factor of 10+ improvements August 6, 2016 - ICHEP L. Barsotti 22
Conclusions Advanced LIGO works, and there are gravitational wave signals out there to detect! Progression of sensitivity improvements interleaved with observing runs in the near future Network of advanced detectors coming on-line in the upcoming years (Virgo, Kagra, LIGO-India) World-wide gravitational wave community working to further extend the reach of ground based detectors, for many events and very high SNR August 6, 2016 - ICHEP L. Barsotti 23
It is just the beginning: the Gravitational Wave Spectrum BH and NS Binaries Cosmic Strings Relic radiation Supernovae Extreme Mass Ratio Inspirals Supermassive BH Binaries Binaries coalescences Spinning NS 10-16 Hz 10-9 Hz 10-4 Hz 10 0 Hz 10 3 Hz Pulsar timing Space detectors Ground interferometers August 6, 2016 - ICHEP L. Barsotti 24
THANKS! August 6, 2016 - ICHEP L. Barsotti 25
GW150914, a discovery in one slide South Pole August 6, 2016 - ICHEP L. Barsotti 26
Advanced LIGO Sensitive Volume Rate roughly 50 BBH mergers each year in a volume of 1 Gpc 3 We can expect 5 or more BBH events in the next observing run About 10 million galaxies per Gpc 3 Advanced LIGO range now ~ 0.1 to 1 Gpc, depending on system mass Initial Range Advanced Range 27
A+: a factor of 2 sensitivity improvement over Advanced LIGO Mature technologies available to reduce quantum noise and improve aligo sensitivity by ~35% beyond design x1.35 3 =2.5 in rate Squeezed light for gravitational wave detectors: Nature Physics 7, 962 965 (2011) Nature Photonics 7, 613 619 (2013) Phys. Rev. Lett. 116, 041102 (2016) Need to reduce thermal noise for maximal benefit: Reducing coating thermal noise as well can lead to a reduction in the noise by a factor of 2 Remember: detection rate scales with cube.. x2 3 = 8 in rate! frequency dependent squeezing experiment @ MIT August 6, 2016 - ICHEP L. Barsotti 28